The present embodiments relate to motion tracking. Tissue moves due to cardiac and/or respiratory forces. In guided medical procedures, tissue motion may negatively affect the procedure. For example, motion may cause application of radiation or therapy to miss, in part, the target.
The adverse effects of the motion may be avoided. For example, in abdominal high intensity focused (HIFU) therapy, the treatment is gated with respiration. A breathing sensor detects the breathing cycle so that treatment is only provided a certain phase of the cycle. In another approach, the patient is asked to hold their breath during treatment to avoid motion. In yet another approach, motion tracking of the tissue may compensate and adjust the procedure to account for the motion, allowing more continuous dosing. If the internal motion is predicted or measured, the therapy dosing may follow the region of interest during the cycle for continuous dosing and corresponding shorter treatment times. For motion tracking, the motion of the tissue itself is tracked. In ultrasound, correlation-based motion estimation is performed. However, tissue-based motion estimation may be prone to error, especially in the presence of non-translational motion, such as rotation, scaling, or deformation.